Fiber optic drop terminals for multiple dwelling units

ABSTRACT

There is provided fiber drop terminals (“FDTs”) and related equipment for providing selective connections between optical fibers of distribution cables and optical fibers of drop cables, such as in multiple dwelling units. The FDTs require relatively little area and/or volume while providing convenient connectivity for a relatively large number of optical connections. The FDTs include adapters for optically connecting the connectors, and the adapters of some FDTs are adapted to rotate, move, or otherwise be removed to provide convenient access for technicians. Some FDTs and the related equipment are adapted for use with microstructured optical fiber having preferred bend characteristics.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to fiber drop terminals, and moreparticularly, to fiber drop terminals defining novel sizes, shapes,and/or functionality.

2. Description of Related Art

To provide improved performance to subscribers, fiber optic networks areincreasingly providing optical fiber connectivity directly to thesubscribers. As part of various fiber-to-the-premises (FTTP),fiber-to-the-home (FTTH), and other initiatives (generally described asFTTx), such fiber optic networks are providing the optical signals fromdistribution cables through local convergence points (“LCPs”) to fiberoptic cables, such as drop cables, that are run directly or indirectlyto the subscribers' premises. Such optical connectivity is increasinglybeing provided to multiple dwelling units (“MDUs”) in part because ofthe relatively large density of subscribers located in an MDU.

MDUs include apartments, condominiums, townhouses, dormitories,hotels/motels, office buildings, factories, and any other collection ofsubscriber locations that are in relatively close proximity to oneanother. MDUs typically are all provided in a single indoor environment,such as an office or condominium; however, MDUs may also include aplurality of individual structures, such as apartment complexes.Typically, if an MDU comprises multiple structures, the optical fibersextending between the structures are adapted for outdoor environments,whereas the optical fibers extending within the structures are adaptedfor indoor environments. Most conventional MDUs include an LCP locatedin a generally central and selectively accessible location, such as thebasement, utility closet, or the like, or the LCP may be located outsidethe MDU on an exterior wall, in a pedestal, in a handhole, or the like.The LCP includes at least one fiber optic cable that optically connectsto a distribution cable. The LCP also includes a connection point wherethe subscriber cables routed through the building are opticallyconnected to the distribution cable.

In some situations the subscriber drop cables are not run directly backto the LCP, but to a fiber drop terminal (also called a fiberdistribution terminal) (“FDT”). FDTs are commonly used in MDUs toprovide optical connectivity between riser cables (generally orientedvertically in the MDU) and the plenum cables (generally orientedhorizontally in the MDU). However, such FDTs are large and are generallynot desirable for installation on each floor or other section of an MDUbased upon the size of their footprint, visibility, and otherconsiderations. Such large FDTs are also relatively expensive to produceand are generally less convenient to transport, install, and service.

Therefore, a need exists for FDTs that provide a require relativelysmall area and/or volume and that provide convenient access fortechnicians. In addition, a need exists for FDTs that provide convenientand secure access to the optical connections within the FDT.

BRIEF SUMMARY OF THE INVENTION

The various embodiments of the present invention address the above needsand achieve other advantages by providing fiber drop terminals (“FDTs”)that are adapted for use with microstructured optical fibers and/orother optical fibers that enable unique size, shapes, features, andother parameters. The FDTs of the present invention provide not only asmall “footprint” (area/volume required for placement of the FDT), butthe FDTs also provide for convenient and secure access to the opticalconnections within the FDT. Still further advantages will be appreciatedby those skilled in the art.

One embodiment of the present invention comprises an FDT adapted for usein a fiber optic network of a multiple dwelling unit to selectivelyoptically connect at least one connectorized optical fiber of adistribution cable to a connectorized optical fiber of at least one dropcable. The FDT comprises a base with a back wall and a sidewallextending outwardly from the back wall, and the base defines at leastone opening for passage of the distribution cable and the drop cable.The FDT also includes a cover that selectively connects to the sidewall.The base of the FDT includes pluralities of adapters that receive aconnector of the distribution cable and a connector of the drop cable tooptically connect the connectorized optical fiber of the distributioncable to the connectorized optical fiber of the drop cable. Thepluralities of adapters are pivotably joined to the base to enable atechnician to move the adapters relative to the base to allow the baseto define a smaller area while still providing convenient access to theadapters, connectors, or other hardware.

Further embodiments of the present invention include FDTs with adistribution cover provided between the base and the cover. Thedistribution cover is adapted to provide limited access to the portionof the adapters that receive a connector of the distribution cable.Therefore, the service provider may prevent unauthorized access to theservice provider side of the FDT. In addition, further embodimentscomprise a removable and/or rotatable bracket for mounting thepluralities of adapters to thereby allow convenient handling of thepluralities of adapters within the FDT.

Still further embodiments of the present invention provide fiber optichardware associated with FDTs and other fiber optic closures. Therefore,the FDTs and associated hardware of various embodiments of the presentinvention provide for convenient and secure optical connectivity whilerequiring relative smaller areas and volumes when compared to prior artclosures.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Having thus described the invention in general terms, reference will nowbe made to the accompanying drawings, which are not necessarily drawn toscale and are meant to be illustrative and not limiting, and wherein:

FIG. 1 is a perspective view of a fiber drop terminal (“FDT”) inaccordance with a first embodiment of the present invention,illustrating the cover selectively removed from the base;

FIG. 2 is a perspective view of the FDT of FIG. 1, illustrating fourpluralities of adapters joined to the back wall of the base and aplurality of openings in the sidewall of the base for passage of fourdistribution cables and 48 drop cables;

FIG. 3 is a perspective view of the four pluralities of adapters of theFDT of FIG. 1, illustrating horizontal hinge at the lower end ofvertical bars to which the pluralities of adapters are connected andillustrating the latch at the upper end of the vertical bars;

FIG. 4 is a perspective view of the four pluralities of adapters of theFDT of FIG. 1, illustrating a first plurality of adapters rotateddownward generally about a horizontal axis;

FIG. 5 is a perspective view of the four pluralities of adapters of theFDT of FIG. 1, illustrating the second plurality of adapters rotateddownward generally about a horizontal axis;

FIG. 6 is a perspective view of the four pluralities of adapters of theFDT of FIG. 1, illustrating the third plurality of adapters rotateddownward generally about a horizontal axis;

FIG. 7 is an enlarged perspective view of the fourth plurality ofadapters of the FDT of FIG. 1, illustrating a bracket at the upper endof the vertical bar, wherein the bracket defines a slot adapted toenable selective rotation of the plurality of adapters about a generallyvertical axis;

FIG. 8 is an enlarged perspective view of the fourth plurality ofadapters of the FDT of FIG. 1, illustrating the vertical barrepositioned relative to the bracket as compared to the view of FIG. 7;

FIG. 9 is an enlarged perspective view of the fourth plurality ofadapters of the FDT of FIG. 1, illustrating the vertical bar rotatedabout a generally vertical axis relative to the view of FIG. 8;

FIG. 10 is schematic view of the bottom of the four pluralities ofadapters of the FDT of FIG. 1, illustrating the horizontal hinge of thethree pluralities of adapters and the bracket of the fourth plurality ofadapters;

FIG. 11 is a perspective view of the FDT of FIG. 1, illustrating thecover selectively attached to the base;

FIG. 12 is a perspective view of an FDT in accordance with a secondembodiment of the present invention, illustrating two pluralities ofadapters and two splice trays mounted to the base, wherein the splicetrays enable splicing of the drop cables to connectorized pigtails;

FIG. 13 is a perspective view of the FDT of FIG. 12, illustrating afirst plurality of adapters rotated downward generally about ahorizontal axis, wherein the latch comprises a fastener for positioningthrough an opening in the vertical bar of the plurality of adapters;

FIG. 14 is a perspective view of the FDT of FIG. 12, illustrating asecond plurality of adapters rotated downward generally about ahorizontal axis;

FIG. 15 is a perspective view of the FDT of FIG. 12, illustrating theselective removal of one splice tray from the base of the FDT;

FIG. 16 is an enlarged perspective view of grommets used in the FDTs ofboth of the embodiments of FIGS. 1 and 12, illustrating a first grommetadapted to receive 12 drop cables and a second grommet (on the right)adapted to receive 24 drop cables;

FIG. 17 is a perspective view of a strain relief device adapted for usewith microstructured optical fiber in accordance with one embodiment ofthe present invention, illustrating the strain relief device within theFDT of FIG. 1 proximate the grommet of FIG. 16;

FIG. 18 is an enlarged perspective view of the strain relief device ofFIG. 17, illustrating the plurality of slots adapted to receive themicrostructured optical fibers;

FIG. 19 is an enlarged perspective view of the strain relief device ofFIG. 17, illustrating a circumferential slot with at least one shoulderadapted to receive and prevent axial movement of a compression device;

FIG. 20 is an enlarged perspective view of the strain relief device ofFIG. 17, illustrating the compression device, comprising a wire tiedevice, provided within the circumferential slot to provide strainrelief to the microstructured optical fibers;

FIG. 21 is a front schematic view of an FDT in accordance with a thirdembodiment of the present invention, illustrating the cover;

FIG. 22 is a perspective view of the FDT of FIG. 21, illustrating theplurality of adapters and the distribution cover provided between theback wall and the cover to provide limited access to the portion of theadapters that are adapted to receive a connector of the distributioncable;

FIG. 23 is a perspective view of the FDT of FIG. 21, illustrating thedistribution cover in an opened position, thus allowing access to theportion of the adapters that are adapted to receive a connector of thedistribution cable;

FIG. 24 is a bottom schematic view of the FDT of FIG. 21, illustratingthe opening in the base for passage of the distribution cable (on theleft) and the opening in the base for passage of the drop cables (on theright);

FIG. 25 is a perspective view of an FDT in accordance with a fourthembodiment of the present invention, illustrating two pluralities ofadapters joined to a bracket that is selectively removable from thebase;

FIG. 26 is a perspective view of the FDT of FIG. 25, illustrating theremoval of the bracket from the base of the FDT;

FIG. 27 is a perspective view of the FDT of FIG. 25, illustrating theselective rotation of the bracket relative to the base of the FDT;

FIG. 28 is a perspective view of a cover adapted to be selectivelyconnected to the base of the FDT of FIG. 25, illustrating the generallydome shape of the cover;

FIG. 29 is a front schematic view of the cover of FIG. 28;

FIG. 30 is a side schematic view of the cover of FIG. 28;

FIG. 31 is a side schematic view of an alternative cover adapted to beselectively connected to the base of an FDT similar to the embodiment ofFIG. 25, illustrating a protruding tab adapted to be received within amating slot in the base of the FDT to selectively retain the coverrelative to the base;

FIG. 32 is a front schematic view of the cover of FIG. 31;

FIG. 33 is a top schematic view of the sidewall of the base of an FDTsimilar to the embodiment of FIG. 25, illustrating one opening forpassage of the distribution cable and plurality of openings for passageof the drop cables;

FIG. 34 is a top schematic view of the sidewall of the base of an FDTsimilar to the embodiment of FIG. 25, illustrating one opening forpassage of the distribution cable and two slots adapted to allow passageof two or more drop cables, wherein each slot defines at least oneopened portion sized to allow passage of a connector of a drop cable andeach slot further defines other portions sized to allow passage of thedrop cable alone;

FIG. 35 is a perspective view of a strain relief device adapted for usewith an opening in an FDT, such as the opening for passage of thedistribution cable in the FDT of FIG. 25, illustrating the generallyfrustoconical shape and the three ribs along the frustoconical surfaceto provide improved strain relief for the distribution cable; and

FIG. 36 is a perspective view of the strain relief device of FIG. 35,illustrating the strain relief device selectively received within theopening of the FDT to seal and strain relieve the distribution cable.

DETAILED DESCRIPTION OF THE INVENTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which some, but not allembodiments of the invention are shown. Indeed, the invention may beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will satisfy applicable legalrequirements. Although apparatus and methods for providing opticalconnectivity between optical fibers of distribution cables and dropcables are described and shown in the accompanying drawings with regardto specific types of fiber drop terminals, also known as fiberdistribution terminals, (collectively, “FDTs”), it is envisioned thatthe functionality of the various apparatus and methods may be applied toany now known or hereafter devised enclosures and related fiber opticnetwork equipment in which it is desired to provide optical connectionsbetween optical fibers of any cables within the fiber optic network.Like numbers refer to like elements throughout.

With reference to FIGS. 1-36, various FDTs and associated equipment inaccordance with some embodiments of the present invention areillustrated. As mentioned above, although these embodiments aredescribed herein as being used as a network access point opticalconnection for distribution cable(s) and drop cables for multipledwelling units (“MDUs”), it should be appreciated that the embodimentsof the present invention may be used at alternative positions within thefiber optic network to connect any optical fibers within the network.Furthermore, although the illustrated embodiments are adapted for usewithin an MDU and do not include much of the standard features ofoutdoor hardware, further embodiments of the present invention includeadditional features, designs, components, and other functionalitiesadapted for use outside an MDU. As described more fully below, theillustrated embodiments of the present invention are described as usingmicrostructured optical fiber; however, further embodiments of thepresent invention are adapted to include any alternative type of opticalfiber. In addition, FDTs of certain embodiments of the present inventioninclude many of the dimensional, functional, design, and other featuresof the fiber distribution terminals (also referred to as “FDTs” andwhich are generally synonymous with fiber drop terminals) disclosed inU.S. patent application Ser. No. 11/653,137 filed on Jan. 12, 2007,which is assigned to the present assignee and the disclosure of which isincorporated in its entirety by reference herein.

Turning now to the embodiment of FIGS. 1-11, an FDT adapted for use in afiber optic network of an MDU is provided. The FDT 10 enables atechnician to selectively optically connect at least one connectorizedoptical fiber of a distribution cable (not shown) to a connectorizedoptical fiber of at least one drop cable (not shown). The FDT comprisesa base 12 defining a back wall 14 and a sidewall 16 extending outwardlyfrom the back wall. The back wall 14 of the illustrated embodimentcomprises a two-part back wall to allow convenient removal of some ofthe hardware therein, whereas further embodiments of the presentinvention may comprise any number of back wall(s). The base 12 of FIGS.1-11 defines four openings 18 for passage of the distribution cables andtwo openings 20 for passage of the drop cables through the sidewall 16.The term “passage” for purposes of this patent application shall includethe passing of continuous optical fibers of the respective cable andshall also include the passage of optical signals communicated throughthe optical fibers even though the actual fiber may be terminated andjoined to a second optical fiber, such as in a connector-adapterinterface, a connector-connector interface, or any other use of opticalwaveguides. Therefore, “passage” of the optical fiber or cable is notlimited to situations where the actual fiber or cable pass into or outof the base; the optical signal need only pass into or out of the basefor there to be “passage.” Referring to FIG. 2, the openings 18 forpassage of the distribution cables comprise a multi-fiber adapter 19 afor receiving a multi-fiber connector of the distribution cable (notshown), whereas the openings 20 for passage of the drop cables comprisegrommets that allow the drop cables to pass directly through. For theembodiment of FIG. 2, a fanout device 19 b is provided to divide theoptical fibers of the multi-fiber adapter 19 a into individual opticalfibers routed to the connectors of the distribution cables describedbelow. Further embodiments of the present invention also provideopenings in the back wall to allow passage of the distribution cable(s)and/or drop cables.

The FDT of FIGS. 1-11 also includes a cover 22 adapted to selectivelyconnect to the sidewall 16 generally opposite the back wall 14; however,further embodiments of the present invention provide the cover at anylocation relative to the back wall. The FDT 10 of FIGS. 1-11 alsocomprises four pluralities of adapters 24 joined to the back wall 14,whereas further embodiments provide the plurality of adapters at anylocation relative to the base and/or cover. The adapters 24 are adaptedto receive a connector 26 of the distribution cable and a connector 28of the drop cable to optically connect the connectorized optical fiberof the distribution cable to the connectorized optical fiber of the dropcable. The pluralities of adapters 24 of FIGS. 1-11 are pivotably joinedto the base 12 to provide convenient access to each of the adapterswhile also allowing a relatively large number of adapters (compared toprior art FDTs) to be provided within the FDT.

Turning again to the cover 22 of FIG. 1, the cover defines a perimeterthat on the top, left, and right sides defines a generallyinwardly-facing groove that is adapted to receive a generallyoutwardly-facing lip 30 of the base to thereby enable the cover toslideably engage the sidewall 16 of the base 12. Further embodiments ofthe present invention include alternative designs to provide a coverthat may be selectively connected to the base and/or that is selectivelyrotatable relative to the base.

Referring now to the pluralities of adapters 24 of the FDT of FIGS.1-11, the adapters 24 are connected with a vertical bar 32 thatcomprises a horizontal hinge 34 at a bottom end of the vertical bar anda latch 36 adapted to enable selective rotation of the plurality ofadapters about a generally horizontal axis. The hinge 34 may permanentlyattach the adapters 24 to the base 12, or the hinge 34 may allowselective removal of the adapters from the base. The latch 36 of theillustrated embodiment comprises two prongs that may be squeezedtogether to allow passage through a narrow slot to disconnect thevertical bar, and the narrow slot may taper inwards so that the verticalbar may be connected without squeezing the prongs together. Stillfurther embodiments of the present invention comprise alternativedevices for providing selectively moveable pluralities of adapters.

The vertical bars 32 of FIG. 3 each connect to twelve SC adapters 24,whereas further embodiments of the present invention connect any numberof fiber optic connectors and any style of optical connectors, includingbut not limited to LC, FC, MTP, and any other single or multiple fiberconnectors for single-mode or multi-mode fiber. The adapters 24 defineaxes that are generally oriented along a plane that is generallyparallel to the back wall of the base to allow the FDT 10 to have agenerally low profile. Although the adapters 24 are illustrated asextending in a generally horizontal direction, further embodiments ofthe present invention provide the adapters in a generally verticaldirection (such that the “vertical” bar becomes “horizontal”). Stillfurther embodiments of the present invention include adapters with axesthat extend in a generally orthogonal direction relative to the backwall of the base and/or in other orientations.

The FDT 10 includes four pluralities of adapters 24, with the firstthree adapters (in order of their ability to be moved to access theplurality of adapters behind) having hinges 34 and latches 36 asdescribed above. Each plurality of adapters 24 is positioned a certaindistance from the back wall 14 to allow each of the pluralities ofadapters to be selectively moved by a technician. As shown in FIG. 7,the fourth plurality of adapters 24 includes a vertical bar 32 that isjoined to the base 14 by a bracket 38 at each end of the vertical bar.The bracket 38 defines a slot 40 adapted to enable selective rotation ofthe plurality of adapters about a vertical axis. The slot 40 receives astandoff device 42, such as a pin, and allows the pin to be moved withinthe slot a certain distance and/or direction to enable the adapters 24(and any connected connectors) to be rotated a sufficient amount toallow convenient access to the adapters without causing the minimum bendradius of the associated optical fiber to be compromised by engaging theback wall 14 or the like. FIG. 9 illustrates the plurality of adapters24 in a rotated position.

Turning now to the embodiment of FIG. 12, the FDT 110 includes similarpluralities of adapters 124, but with alternative devices for allowingselective movement of the pluralities of adapters. The pluralities ofadapters 124 include a vertical bar 132 and a hinge 134; however, thelatch 136 comprises an opening for receiving a fastening device, such asa screw, nut/bolt combination, wire tie, or the like. FIGS. 13 and 14illustrate rotation of the pluralities of adapters 124 about the hinge134. The FDT 110 of FIGS. 12-15 also includes two splice trays 150 thatare mounted to the base 112 to enable splicing an optical fiber of thedrop cable to a connectorized pigtail (the connector 128 is part of thepigtail, which is not otherwise shown). The splice trays are of the typedescribed in the concurrently filed U.S. Patent Application entitled“Fiber Optic Splice Trays” that is assigned to the present assignee andthe disclosure of which is incorporated by reference in its entiretyherein. The splice tray 150 of the illustrated embodiment includes aslot 152 to selectively receive a tab 154 protruding from the back wall114 of the base 112 to enable selective mounting of the splice tray tothe base. Still further embodiments of the present invention comprisealternative devices for mounting one or more splice trays to the base.Still further embodiments of the present invention include FDTs withsplitter devices provided within the FDT and other fiber optic hardwareas desired.

FIG. 16 provides an enlarge view of the grommets 160 and 162 provided inthe openings 20 of the FDT 10 of FIGS. 1-11, and also provided on theFDT 110 of FIGS. 12-15. The grommet 160 comprises twelve openings 164for passage of twelve individual drop cables (not shown), and thegrommet 162 comprises twenty-four openings 164 for passage oftwenty-four individual drop cables. The openings 164 include slots 166so that the cables may be placed within in the grommet without passingan end of the drop cable (which may or may not have a connector attachedto the end) through the hole, thus making installation of the grommetmore convenient. Alternative embodiments of the present inventioncomprise alternative grommets for generally sealing and retaining theopenings in the base and/or cover of the FDT that allow passage of thefiber optic cables.

FIGS. 17-20 illustrate a strain relief device 170 included in certainembodiments of the present invention. The strain relief device 170 isadapted for use with microstructured optical fibers, as described morefully below, based upon the ability of such fibers to withstand agreater compression without causing excessive signal loss within thefiber. The strain relief device 170 comprises a body 172 with agenerally cylindrical shape that defines an axis generally aligned withthe axis of the microstructured optical fibers 174 to be strainrelieved. Along the perimeter of the body 172 are provided a pluralityof slots 176 adapted to receive the microstructured optical fibers 174(and any tubes, cables, or other assemblies associated therewith) suchthat a portion of the microstructured optical fibers is positionedradially outward of the perimeter of the body. Once the microstructuredoptical fibers are positioned within the slots 176 of the body 172, acompression device 178 is positioned around the body 172 and themicrostructured optical fibers 174 to apply a force upon themicrostructured optical fibers to strain relieve the optical fibers. Thebody 170 defines a circumferential slot 180 adapted to receive thecompression device 178. The slot 178 defines at least one shoulder 182to prevent axial movement of the compression device 178. The compressiondevice 178 of the illustrated embodiment comprises a wire tie device;however, further embodiments of the present invention comprisealternative compression devices to retain and/or seal the optical fibersto the strain relief device. As shown in FIG. 17, the FDT 10 or otherenclosure into which the strain relief device 170 is installed mayinclude a spring clip 184 mounted to a surface (such as the back wall14) to selectively retain the strain relief device relative to the FDTor other enclosure. Further embodiments of the present invention includealternative devices for retaining the strain relief device relative tothe fiber optic enclosure.

Turning now to FIGS. 21-24, the FDT 210 is yet another embodiment of thepresent invention that provides selective optical connectivity forconnectorized optical fibers of a distribution cable and connectorizedoptical fibers of drop cables. The FDT comprises a base 212 defining aback wall 214 and a sidewall 216 extending outwardly from the back wallsimilar to the embodiment of FIG. 1. The FDT 210 also includes aplurality of adapters 224 joined to the base 212, and includes adistribution cover 250 between the back wall 214 of the base 212 and thecover 222. The distribution cover 250 is adapted to provide limitedaccess to the portion of the adapters 224 that receive a connector 226of the distribution cable. The distribution cover 250 of someembodiments of the present invention includes a lock device, such as afastener with an uncommon feature, a padlock, or the like, to allowaccess under the distribution cover to only limited individuals, such astechnicians working on behalf of the service provider, thus preventingtampering with the optical connections by customers, vandals, or others.

Although not shown in FIGS. 21-24, the FDT 210 includes grommets orsimilar devices in the openings 218 and 220, and may include a fanoutpositioned between the distribution cover and the base to opticallyconnect the optical fiber of the distribution cable with the portion ofthe adapters that receive a connector 226 of the distribution cable. Theplurality of adapters 224 of the FDT 210 are illustrated in a fixedposition relative to the base 212 of the FDT; however, furtherembodiments of the present invention may include additional oralternative features to allow the plurality of adapters to be moved asdesired.

Turning now to FIGS. 25-38, an FDT in accordance with yet anotherembodiment of the present invention is illustrated. The FDT 310 definesa generally curved top and front surface (on both the cover 322 andsidewalls 316 of the base 312). The FDT 310 also includes a bracket 332that is selectively movable relative to the base 312 and to which arejoined two pluralities of adapters 324. The bracket 332 is selectivelyremovable from the base 312, as shown in FIG. 26, and is selectivelyrotatable relative to the base 312, as shown in FIG. 27. The bracket 332comprises a polymer or other moderately flexible material to allowsufficient bending, when a force is exerted upon the bracket by atechnician with his or hand or with a tool or the like, to cause thebracket 332 to become detached at one or more attachment points. Asshown in FIGS. 25-27, the bracket 332 is attached to the base 312 atfour points with pins 333 a that are received in openings 333 b onprotrusions from the base. Therefore, a technician can detach all fourpins 333 a to selectively remove the bracket 333, or detach the two toppins 333 a to selective rotate the bracket about a horizontal axis, orthe like. Further embodiments of the present invention includeadditional brackets attached/detached by alternative devices that may beremoved and/or rotated in alternative directions.

The two pluralities of adapters 324 each define axes of the adapterstherein, and the FDT 310 of FIG. 25 includes pluralities of adapters 324that are slightly angled relative to one another to enable convenientaccess to one or both sides of the adapters. Further embodiments of thepresent invention include alternative numbers of adapters at alternativerelative positions and/or orientations. As shown in FIGS. 28-32, the FDT310 includes a cover 322 that is generally domed shape. The cover 322 ofFIGS. 31 and 32 comprises a latch device 323 a on each side of the covergenerally near the bottom of the cover to selectively retain the coverrelative the base. The base 312 of an FDT (as shown in FIG. 34) isadapted to receive the cover 322 of FIGS. 31 and 32 includes an opening323 b for each latch device 323 a to selective receive the latch deviceand retain the cover relative to the base.

Turning now to FIGS. 33 and 34, a top view of the sidewall 316 of theFDT 310 is provided. As can be seen, the opening 318 for passage of thedistribution cable (not shown) can include an adapter 319 a. Theopenings 320 a for the drop cables may include grommets 360 as shown inFIG. 33. Alternatively, as shown in FIG. 34, the openings 320 b maydefine one or more slots adapted to allow passage of two or more dropcables. The slot defines at least one opened portion 320 c sized toallow passage of the connector of the drop cable, and the slot furtherdefines other portions 320 d and 320 e sized to allow passage of thedrop cable alone. Still further embodiments of the present inventioncomprise alternative openings and structures for providing secure andconvenient passage of the optical fibers and/or cables into the FDT.

Referring now to FIGS. 35 and 36, a strain relief device 370 is providedto strain relieve and seal a distribution cable through an opening 318within the FDT. The strain relief device comprises a generallyfrustoconical device that includes three ribs 371 along thefrustoconical surface 373. The ribs 371 enable the strain relief device370 to be better retained within the opening 318 (as compared to similardevices without ribs), and the frustoconical surface 373 enables thestrain relief device to be wedged within the opening to provide asufficient seal and/or sufficient strain relief. The strain reliefdevice 370 includes a slit along the axial length of the strain reliefdevice to provide convenient receipt of the cable within the strainrelief device. Still further embodiments of the present inventioninclude alternative strain relief devices.

Various embodiments of the present invention are adapted to include bendperformance optical fibers. One example of bend performance opticalfiber is a microstructured optical fiber having a core region and acladding region surrounding the core region, the cladding regioncomprising an annular hole-containing region comprised ofnon-periodically disposed holes such that the optical fiber is capableof single mode transmission at one or more wavelengths in one or moreoperating wavelength ranges.

The core region and cladding region provide improved bend resistance,and single mode operation at wavelengths preferably greater than orequal to 1500 nm, in some embodiments also greater than about 1310 nm,in other embodiments also greater than 1260 nm. The optical fibersprovide a mode field at a wavelength of 1310 nm preferably greater than8.0 microns, more preferably between about 8.0 and 10.0 microns. Inpreferred embodiments, optical fiber disclosed herein is thussingle-mode transmission optical fiber.

In some embodiments of the present invention, the microstructuredoptical fibers disclosed herein comprises a core region disposed about alongitudinal centerline and a cladding region surrounding the coreregion, the cladding region comprising an annular hole-containing regioncomprised of non-periodically disposed holes, wherein the annularhole-containing region has a maximum radial width of less than 12microns, the annular hole-containing region has a regional void areapercent of less than about 30 percent, and the non-periodically disposedholes have a mean diameter of less than 1550 nm.

By “non-periodically disposed” or “non-periodic distribution”, it ismeant that when one takes a cross-section (such as a cross-sectionperpendicular to the longitudinal axis) of the optical fiber, thenon-periodically disposed holes are randomly or non-periodicallydistributed across a portion of the fiber. Similar cross sections takenat different points along the length of the fiber will reveal differentcross-sectional hole patterns, i.e., various cross-sections will havedifferent hole patterns, wherein the distributions of holes and sizes ofholes do not match. That is, the holes are non-periodic, i.e., they arenot periodically disposed within the fiber structure. These holes arestretched (elongated) along the length (i.e. in a direction generallyparallel to the longitudinal axis) of the optical fiber, but do notextend the entire length of the entire fiber for typical lengths oftransmission fiber.

For a variety of applications, it is desirable for the holes to beformed such that greater than about 95% of and preferably all of theholes exhibit a mean hole size in the cladding for the optical fiberwhich is less than 1550 nm, more preferably less than 775 nm, mostpreferably less than 390 nm. Likewise, it is preferable that the maximumdiameter of the holes in the fiber be less than 7000 nm, more preferablyless than 2000 nm, and even more preferably less than 1550 nm, and mostpreferably less than 775 nm. In some embodiments, the fibers disclosedherein have fewer than 5000 holes, in some embodiments also fewer than1000 holes, and in other embodiments the total number of holes is fewerthan 500 holes in a given optical fiber perpendicular cross-section. Ofcourse, the most preferred fibers will exhibit combinations of thesecharacteristics. Thus, for example, one particularly preferredembodiment of optical fiber would exhibit fewer than 200 holes in theoptical fiber, the holes having a maximum diameter less than 1550 nm anda mean diameter less than 775 nm, although useful and bend resistantoptical fibers can be achieved using larger and greater numbers ofholes. The hole number, mean diameter, max diameter, and total void areapercent of holes can all be calculated with the help of a scanningelectron microscope at a magnification of about 800× and image analysissoftware, such as ImagePro, which is available from Media Cybernetics,Inc. of Silver Spring, Md., USA.

The optical fibers disclosed herein may or may not include germania orfluorine to also adjust the refractive index of the core and or claddingof the optical fiber, but these dopants can also be avoided in theintermediate annular region and instead, the holes (in combination withany gas or gases that may be disposed within the holes) can be used toadjust the manner in which light is guided down the core of the fiber.The hole-containing region may consist of undoped (pure) silica, therebycompletely avoiding the use of any dopants in the hole-containingregion, to achieve a decreased refractive index, or the hole-containingregion may comprise doped silica, e.g. fluorine-doped silica having aplurality of holes.

In one set of embodiments, the core region includes doped silica toprovide a positive refractive index relative to pure silica, e.g.germania doped silica. The core region is preferably hole-free. In someembodiments, the core region comprises a single core segment having apositive maximum refractive index relative to pure silica Δ₁ in %, andthe single core segment extends from the centerline to a radius R1. Inone set of embodiments, 0.30%<Δ₁<0.40%, and 3.0 μm<R1<5.0 μm. In someembodiments, the single core segment has a refractive index profile withan alpha shape, where alpha is 6 or more, and in some embodiments alphais 8 or more. In some embodiments, the inner annular hole-free regionextends from the core region to a radius R2, wherein the inner annularhole-free region has a radial width W12, equal to R2−R1, and W12 isgreater than 1 μm. Radius R2 is preferably greater than 5 μm, morepreferably greater than 6 μm. The intermediate annular hole-containingregion extends radially outward from R2 to radius R3 and has a radialwidth W23, equal to R3−R2. The outer annular region 186 extends radiallyoutward from R3 to radius R4. Radius R4 is the outermost radius of thesilica portion of the optical fiber. One or more coatings may be appliedto the external surface of the silica portion of the optical fiber,starting at R4, the outermost diameter or outermost periphery of theglass part of the fiber. The core region and the cladding region arepreferably comprised of silica. The core region is preferably silicadoped with one or more dopants. Preferably, the core region ishole-free. The hole-containing region has an inner radius R2 which isnot more than 20 μm. In some embodiments, R2 is not less than 10 μm andnot greater than 20 μm. In other embodiments, R2 is not less than 10 μmand not greater than 18 μm. In other embodiments, R2 is not less than 10μm and not greater than 14 μm. Again, while not being limited to anyparticular width, the hole-containing region has a radial width W23which is not less than 0.5 μm. In some embodiments, W23 is not less than0.5 μm and not greater than 20 μm. In other embodiments, W23 is not lessthan 2 μm and not greater than 12 μm. In other embodiments, W23 is notless than 2 μm and not greater than 10 μm.

Such fiber can be made to exhibit a fiber cutoff of less than 1400 nm,more preferably less than 1310 nm, a 20 mm macrobend induced loss at1550 nm of less than 1 dB/turn, preferably less than 0.5 dB/turn, evenmore preferably less than 0.1 dB/turn, still more preferably less than0.05 dB/turn, yet more preferably less than 0.03 dB/turn, and even stillmore preferably less than 0.02 dB/turn, a 12 mm macrobend induced lossat 1550 nm of less than 5 dB/turn, preferably less than 1 dB/turn, morepreferably less than 0.5 dB/turn, even more preferably less than 0.2dB/turn, still more preferably less than 0.01 dB/turn, still even morepreferably less than 0.05 dB/turn, and a 8 mm macrobend induced loss at1550 nm of less than 5 dB/turn, preferably less than 1 dB/turn, morepreferably less than 0.5 dB/turn, and even more preferably less than 0.2dB-turn, and still even more preferably less than 0.1 dB/turn.

The fiber of some embodiments of the present invention comprises a coreregion that is surrounded by a cladding region that comprises randomlydisposed voids which are contained within an annular region spaced fromthe core and positioned to be effective to guide light along the coreregion. Other optical fibers and microstructured fibers may be used inthe present invention. Additional features of the microstructuredoptical fibers of additional embodiments of the present invention aredescribed more fully in pending U.S. patent application Ser. No.11/583,098 filed Oct. 18, 2006, and provisional U.S. patent applicationSer. No. 60/817,863 filed Jun. 30, 2006; U.S. patent application Ser.No. 60/817,721 filed Jun. 30, 2006; U.S. patent application Ser. No.60/841,458 filed Aug. 31, 2006; and U.S. Patent application Ser. No.60/841,490 filed Aug. 31, 2006; all of which are assigned to CorningIncorporated and the disclosures of which are incorporated by referenceherein.

Many modifications and other embodiments of the invention set forthherein will come to mind to one skilled in the art to which theinvention pertains having the benefit of the teachings presented in theforegoing descriptions and the associated drawings. Therefore, it is tobe understood that the invention is not to be limited to the specificembodiments disclosed and that modifications and other embodiments areintended to be included within the scope of the appended claims. It isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents. Although specific terms areemployed herein, they are used in a generic and descriptive sense onlyand not for purposes of limitation.

1. A fiber drop terminal (“FDT”) adapted for use in a fiber opticnetwork of a multiple dwelling unit to selectively optically connect atleast one connectorized optical fiber of a distribution cable to aconnectorized optical fiber of at least one drop cable, the FDTcomprising: a base defining a back wall and at least one sidewallextending outwardly from the back wall, wherein the base defines atleast one opening for passage of the distribution cable and the dropcable through at least one of the back wall and sidewall; a coveradapted to selectively connect to the sidewall generally opposite theback wall; and at least one plurality of adapters joined to at least oneof the back wall and the sidewall of the base, wherein the adapters areadapted to receive a connector of the distribution cable and a connectorof the drop cable to optically connect the connectorized optical fiberof the distribution cable to the connectorized optical fiber of the dropcable; wherein the plurality of adapters is pivotably joined with abracket mounted to the base.
 2. An FDT according to claim 1, wherein thecover slideably engages the sidewall of the base.
 3. An FDT according toclaim 1, wherein the cover is rotatably connected to the sidewall of thebase.
 4. An FDT according to claim 1, wherein the plurality of adaptersare connected with a vertical bar, and wherein the vertical barcomprises a horizontal hinge and a latch adapted to enable selectiverotation of the plurality of adapters about a generally horizontal axis.5. An FDT according to claim 4, wherein the horizontal hinge is providedat a bottom end of the vertical bar and the latch is provided at a topend of the vertical bar.
 6. An FDT according to claim 1, wherein theplurality of adapters are connected with a vertical bar, and wherein thevertical bar is joined to the base by a bracket at each end of thevertical bar, and wherein the bracket defines a slot adapted to enableselective rotation of the plurality of adapters about a generallyvertical axis.
 7. An FDT according to claim 1, wherein the at least oneplurality of adapters comprises a first plurality of adapters connectedwith a vertical bar and a second plurality of adapters connected with avertical bar, and wherein the first plurality of adapters are provided afirst distance from the back wall and the second plurality of adaptersare provided a second distance from the back wall, the first distancebeing different than the second distance.
 8. An FDT according to claim 1further comprising a splice tray mounted to the base to enable splicingto a connectorized pigtail of at least one of an optical fiber of thedistribution cable and an optical fiber of the drop cable.
 9. An FDTaccording to claim 8, wherein the splice tray comprises a slot toselectively receive a tab protruding from the back wall of the base toenable selective mounting of the splice tray to the base.
 10. An FDTaccording to claim 1, wherein the at least one opening of the basecomprises an opening adapted to receive a multi-fiber adapter.
 11. AnFDT according to claim 10 further comprising a fanout device tooptically connect the multi-fiber adapter to the plurality of adapters.12. An FDT according to claim 1, wherein the at least one opening of thebase comprises an opening adapted to receive a grommet comprising anopening for each of the drop cables.
 13. An FDT according to claim 1,wherein the plurality of adapters define axes that are generallyoriented along a plane generally parallel to the back wall of the base.14. An FDT according to claim 1, wherein plurality of adapters defineaxes that are generally orthogonal to the back wall of the base.
 15. AnFDT according to claim 1, wherein the FDT is adapted to receive at leastone optical fiber comprising a microstructured optical fiber comprisinga core region and a cladding region surrounding the core region, thecladding region comprising an annular hole-containing region comprisedof non-periodically disposed holes.
 16. An FDT according to claim 15,wherein the microstructured fiber has an 8 mm macrobend induced loss at1550 nm of less than 0.2 dB/turn.
 17. A strain relief device adapted foruse with microstructured optical fiber, the strain relief devicecomprising: a body defining an axis generally aligned with the axis ofthe microstructured optical fibers to be strain relieved; a plurality ofslots adapted to receive the microstructured optical fibers; and acompression device adapted for positioning around the body and themicrostructured optical fibers received within the plurality of slots toapply a force upon the microstructured optical fibers to strain relievethe optical fibers.
 18. A strain relief device according to claim 17,wherein the body defines a generally cylindrical shape.
 19. A strainrelief device according to claim 17, wherein the plurality of slots isdefined along the perimeter of the body such that a portion of themicrostructured optical fibers is positioned radially outward of theperimeter of the body.
 20. A strain relief device according to claim 17,wherein the body defines a circumferential slot adapted to receive thecompression device, wherein the slot defines at least one shoulder toprevent axial movement of the compression device.
 21. A strain reliefdevice according to claim 17, wherein the compression device comprises awire tie device.
 22. A strain relief device according to claim 17further comprising a spring clip to selectively mount the strain reliefdevice within a fiber optic enclosure.
 23. A strain relief deviceaccording to claim 17, wherein the FDT is adapted to receive at leastone optical fiber comprising a microstructured optical fiber comprisinga core region and a cladding region surrounding the core region, thecladding region comprising an annular hole-containing region comprisedof non-periodically disposed holes.
 24. A strain relief device accordingto claim 23, wherein the microstructured fiber has an 8 mm macrobendinduced loss at 1550 nm of less than 0.2 dB/turn.
 25. A fiber dropterminal (“FDT”) adapted for use in a fiber optic network of a multipledwelling unit to selectively optically connect at least oneconnectorized optical fiber of a distribution cable to a connectorizedoptical fiber of at least one drop cable, the FDT comprising: a basedefining a back wall and at least one sidewall extending outwardly fromthe back wall, wherein the base defines at least one opening for passageof the distribution cable and the drop cable through at least one of theback wall and sidewall; a cover adapted to selectively connect to thesidewall generally opposite the back wall; at least one plurality ofadapters joined to at least one of the back wall and the sidewall of thebase, wherein the adapters are adapted to receive a connector of thedistribution cable and a connector of the drop cable to opticallyconnect the connectorized optical fiber of the distribution cable to theconnectorized optical fiber of the drop cable; and a distribution coverprovided between the back wall and the cover, wherein the distributioncover is adapted to provide limited access to the portion of theadapters that are adapted to receive a connector of the distributioncable.
 26. An FDT according to claim 25, wherein the cover is rotatablyattached to the base and the distribution cover is rotatably attached tothe base.
 27. An FDT according to claim 25 further comprising a fanoutpositioned between the distribution cover and the base and opticallyconnecting the optical fiber of the distribution cable with the portionof the adapters that are adapted to receive a connector of thedistribution cable.
 28. An FDT according to claim 25, wherein the atleast one opening of the base comprises an opening adapted to receive amulti-fiber adapter.
 29. An FDT according to claim 25, wherein the atleast one opening of the base comprises an opening adapted to strainrelieve and seal the drop cables passing therethrough.
 30. An FDTaccording to claim 25, wherein the FDT is adapted to receive at leastone optical fiber comprising a microstructured optical fiber comprisinga core region and a cladding region surrounding the core region, thecladding region comprising an annular hole-containing region comprisedof non-periodically disposed holes.
 31. An FDT according to claim 30,wherein the microstructured fiber has an 8 mm macrobend induced loss at1550 nm of less than 0.2 dB/turn.
 32. A fiber drop terminal (“FDT”)adapted for use in a fiber optic network of a multiple dwelling unit toselectively optically connect at least one connectorized optical fiberof a distribution cable to a connectorized optical fiber of at least onedrop cable, the FDT comprising: a base defining a back wall and at leastone sidewall extending outwardly from the back wall, wherein the basedefines at least one opening for passage of the distribution cable andthe drop cable through at least one of the back wall and sidewall; acover adapted to selectively connect to the base; and at least oneplurality of adapters joined to a bracket attached to at least one ofthe back wall and the sidewall of the base, wherein the adapters areadapted to receive a connector of the distribution cable and a connectorof the drop cable to optically connect the connectorized optical fiberof the distribution cable to the connectorized optical fiber of the dropcable; wherein the bracket is selectively movable relative to the base.33. An FDT according to claim 32, wherein the bracket is selectivelydetachable from the base.
 34. An FDT according to claim 32, wherein thebracket is selectively rotatable relative to the base.
 35. An FDTaccording to claim 34, wherein the bracket is selectively rotatableabout a horizontal axis.
 36. An FDT according to claim 32, wherein theat least one plurality of adapters comprises a first plurality ofadapters and a second plurality of adapters joined to the bracket, andwherein the first plurality of adapters define axes that are angledrelative to axes of the second plurality of adapters.
 37. An FDTaccording to claim 32, wherein the cover generally defines a dome. 38.An FDT according to claim 32, wherein the cover comprises at least onelatch device adapted to selectively retain the cover relative the base.39. An FDT according to claim 32, wherein the at least one opening ofthe base comprises one opening for the distribution cable and aplurality of openings for the drop cables.
 40. An FDT according to claim32, wherein the at least one opening of the base comprises at least oneslot adapted allow passage of two or more drop cables.
 41. An FDTaccording to claim 40, wherein the slot defines at least one openedportion sized to allow passage of the connector of the drop cable andthe slot further defines other portions sized to allow passage of thedrop cable alone.
 42. An FDT according to claim 32 further comprising astrain relief device adapted to be selectively received in the openingof the base and adapted to strain relieve and seal at least one of thedistribution cable and the drop cable.
 43. An FDT according to claim 42,wherein the strain relief device comprises a generally frustoconicaldevice defining at least one rib along a frustoconical surface.